System of electrical distribution.



No. 7l2,050. Patentad Oct. 28, I902.

H. EDWARDS.

SYSTEM OF ELECTRICAL DISTRIBUTION.

(Application dim In. so, 1901.;

- (No Modal.)

lnvenKor Harold Edwards y Atty.

lllI lll Witnesses.

UNITED STATES PATENT OFFICE.

HAROLD EDWARDS, OF SOIIENEOTADY, NEIV YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

SYSTEM OF ELECTRICAL DISTRIBUTION.

SPECIFICATION forming part of Letters Patent No. 712,050, dated October 28, 1902.

Application filed March 30. 1901. Serial No. 53,633. (No model.)

To all whom, it may concern:

Be it known that I, HAROLD EDWARDS, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Systems of Electrical Distribution, (Case No. 2,077,) of which the following is a specification.

In many cases it is exceedingly desirable IO that the external characteristic of boosters used in connection with electric circuits should be as straight as possiblein other words, that the boosting effect should vary as nearly as possible in proportion to the current 1 5 flowing through the booster. In practice it has been found that even when the magnetic field of the booster is worked upon that portion of the saturation-curve below the knee the desired straightness of the characteristic curve is not attained, thereby resulting in unsatisfactory operation of the line or lines to which the booster may be connected. Thus if the boosting effect at full load is adjusted to the proper amount then due to the hump of greater or less extent in the characteristic curve the boosting effect at half-load is too great, while if, on the other hand, the adjustments are made properlyfor half-load then at full load the boosting effect is insuliicient.

0 I have discovered that the defect referred to may be remedied by impressing upon the field of the booster a supplementary auxiliary magnetomotive force which varies in a proportion different from the variation of current in the booster itself.

The voltage of the ordinary series-wound booster is proportional to something less than the first power of its current or excitation, while its output is nearlyproportional to the second power of the current or excitation. Since the power-input of the motor driving the booster is substantially the same as the power-output of the booster, the current of the driving-motor will be nearly proportional 5 to the second power of the current of the booster. By making the excitation of the booster proportional to some quantity intermediate between the first and second powers of the booster current the voltage of the booster may be made to rise at a rate faster than the rise of current in the booster, thereby taking the curve out of the boostercharacteristic, or even causing it to bend upward.

Since, as has been seen, the current of the driving-motor varies approximately in pro portion to the second power of the currentin the booster, I may produce in the field of the booster are sultant magnetomotive force proportional to a quantity intermediate between the first and second powers of the booster 60. current by providing the booster-field with a supplementary winding and passing a greater or less proportion of the motor current through said winding.

For a better understanding of my invention reference is to be had to the following description, taken in connection with the accompanying drawings, in which Figure 1 represents in diagram one embodiment of my invention, while Fig. 2 is a diagram explanatory thereof.

As to the scope of the invention, attention is directed more particularly to the claims appended hereto.

In the drawings, 1 represents, conventionally, any suitable source of current feeding supply-mains 2 and 3, to which translating devices at of any desired character are connected either directly or indirectly.

At 5 is represented a series-wound booster having its armature 6 and series field 7 connected in series with each other and with one of the mains 2 3as, for example, the main 3. This booster is mechanically driven by a suitable motor-as, for example, the shunt-woun d motor 8-in this case shown as connected with its armature on the same shaft with or a continuation of the shaft of the armature of the booster 5. The armature of the motor 8 is indicated at 0 and carries a commutator 10, upon which bear commutator-brushes in the usual manner. These com mutator-brushes 11 and 12 are connected to the terminals of the shunt-field 13, current being supplied to the field and armature circuits through con- 5 nections with the mains 2 3 at the points 14 and 15, as indicated.

Current instead of passing directly from the main 2 to the motor 8, as heretofore, is in this case caused to pass through the auxiliary I00 winding 16 on the field-magnet of the booster 5. The amount of current in this auxiliary winding may be adjusted in any suitable manner-as, for example, by varying its number of effective turns or by the employment of an adjusting-shunt or any other well-known means.

With the arrangement of circuits indicated it will be seen that the field of the booster is acted upon by two magnetomotive forces, one of which varies in proportion to the current in the booster and the other in proportion to the current supplied to the motor. The current in the booster if acting alone would not cause a sufficient increasein the field of the booster to prevent a drooping of thecharacteristic curve as the load comes on, while if the auxiliary winding 16, fed with the motor-current, were to act alone it would cause the field of the booster to increase in such a manner as to give an upward bend to the characteristic curve. Therefore by combining the effects of each in suitable proportions, to be determined by calculation and trial in each particular case, the characteristic curve of the booster may be given any desired shape-either straight, bending upward, or a magnified drooping.

With the arrangement so far as above described it will be observed that when no current is passing through the booster-armature there will nevertheless be an electromotive force produced thereby due to the combined effect of residual magnetism, as well as the magnetization due to the small current flowing through the coil 16 in circuit with the driving-motor 8. To neutralize this'electromotive force, I provide a constantly-excited diife'rential winding 17, which, as a matter of convenience, may be excited by being connected in series with the field of the motor, as shown.

Theinterrelation of the effects produced by the various windings of the booster may, perhaps,be better understood by reference to Fig. 2, which represents in a general way the phenomena referred to. The various curves shown indicate by their abscissze certain values of current and by their ordinates corresponding values of electromotive force of the booster. The dotted curve 18 is the characteristic which would be produced by the series winding 7 of the booster acting alone. The dotted curve 19 is the characteristic which would be produced by the winding 16, carrying the current of the driving-motor, while the horizontal line 20 indicates the demagnetizing effect of the coil 17. The combined eifect of the coils 7 and 16 may be represented bycombining their respective curves 18 and 19, which produces the resulting characteristic 21, which is substantially a straight line. Tomake this line start from the origin,

the deinagnetiziug-coil 17 is employed, which when no current is flowing in the distribution system counteracts the combined efiect of residual magnetism and the magnetizing effect of the coil 16, thereby making the electromotive force of the booster zero when the load is zero. The resulting characteristic of the booster is therefore approximately, if not exactly, a straight line, as indicated at 22.

Although I have shown my invention as embodied in a single arrangement of circuits, I do not wish to be limited to the precise arrangement shown, since various modifications of the same may be made without departing from the spirit of my invention.

What I claim as new, and desire to secure by Letters Patent of the United States, is

1. The combination of a booster, and auxiliary means for straightening the external characteristic of said booster.

2. The combination of a motordriven booster, and means for causing its field excitation to vary in a proportion greater than the proportion of variation of current in the booster-circuit.

3. The combination of a series wound booster, a motor for driving the same, and a winding on said booster fedby current passing through said motor.

4:. The combination of a booster, a motor mechanically coupled thereto, and a winding on said booster in circuit with said motor.

5. The combination of a series wound booster, a motor connected thereto, said motor having a field-winding in shunt with its armature-circuit, and an auxiliary winding 'on said booster in circuit with said motor.

6. A motor-driven booster having a plurality of field-windings, one in series with the armature of the booster and another in series with the motor.

7. A motor-driven booster having a plurality of field-windings, one in series with the armature of the booster and another carrying current flowing through said motor.

8. A motor-driven booster having a plurality of field-windings, one of which is in series with the armature of the booster, another in series with the driving-motor, and a third constantly excited from a suitable source.

9. A motor-driven booster having a plurality of field-windings, one of which is in series with the armature of the booster, another in series with the driving-motor, and a third in series with the field-winding of said motor.

10. The combination with the armature of a booster, of a field-magnet, and means for exciting the field-magnet by the resultant of three magnetomotive forces, one of which varies in proportion to current passing through the armature of the booster, another in a greater proportion, and a third of substantially constant value but acting inversely with respect to the other magnetomotive forces.

In witness whereof I have hereunto set my hand this 29th day of March, 1901.

HAROLD EDWARDS.

Witnesses:

BENJAMIN B. HULL, MARGARET E. WOOLLEY. 

